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Free volume theory of diffusion: Method of predicting activation energies of diffusion for gases in elastomers
Author(s) -
Kosiya Rochana,
McGregor Ralph
Publication year - 1981
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1981.070260222
Subject(s) - elastomer , thermodynamics , activation energy , diffusion , arrhenius equation , polymer , materials science , relaxation (psychology) , gaseous diffusion , amorphous solid , glass transition , polymer chemistry , chemistry , organic chemistry , composite material , physics , psychology , social psychology , electrode
It is well established that diffusion and relaxation processes in polymers above T g are closely related in that they are both governed by the polymer segmental motions, which are believed to be determined by the free volume present in the system. The diffusion coefficients of gases in elastomers can be accounted for by the WLF equation using the “universal values” of constants A and B . The parameter K = B D / B η of Frisch and Rogers is used as a correction factor. An analysis has been made of the diffusion of five gases in nine elastomers, from data found in the literature. K and log D g are shown to vary with the penetrant but not with the polymer. Therefore, once the values of K and log D g of gases are determined, their diffusion coefficients in any elastomers of known T g at a variety of temperatures can be estimated. From the Arrhenius and the WLF relationships, an equation is derived to predict the activation energy of diffusion directly from the temperature of diffusion, the glass transition temperature of the amorphous polymer, the predetermined value of K , and the universal constants A and B . In the systems studied, the predictions agree on the average to within 11–17% of the values calculated from the experimental data.